U.S. patent number 8,747,672 [Application Number 13/675,804] was granted by the patent office on 2014-06-10 for process and system for recovering phosphorus from wastewater.
This patent grant is currently assigned to Multiform Harvest Inc.. The grantee listed for this patent is Multiform Harvest Inc.. Invention is credited to Keith E. Bowers.
United States Patent |
8,747,672 |
Bowers |
June 10, 2014 |
Process and system for recovering phosphorus from wastewater
Abstract
Methods and systems for recovery of phosphorus from wastewater
and producing inorganic phosphorus complexes.
Inventors: |
Bowers; Keith E. (Seattle,
WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Multiform Harvest Inc. |
Seattle |
WA |
US |
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Assignee: |
Multiform Harvest Inc.
(Seattle, WA)
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Family
ID: |
44915006 |
Appl.
No.: |
13/675,804 |
Filed: |
November 13, 2012 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130196403 A1 |
Aug 1, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/US2011/036514 |
May 13, 2011 |
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61334328 |
May 13, 2010 |
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61378300 |
Aug 30, 2010 |
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Current U.S.
Class: |
210/607; 210/175;
210/903; 210/749; 210/743; 210/181; 210/906; 210/768 |
Current CPC
Class: |
C02F
1/5254 (20130101); C01B 25/451 (20130101); C12P
3/00 (20130101); C12M 47/10 (20130101); C02F
2209/06 (20130101); Y02W 10/10 (20150501); C02F
2209/02 (20130101); C02F 11/12 (20130101); C02F
3/28 (20130101); C02F 1/28 (20130101); C02F
2101/105 (20130101); C02F 11/04 (20130101) |
Current International
Class: |
C02F
3/00 (20060101) |
Field of
Search: |
;210/607,768,175,903,906,749,743,181 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 698 595 |
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Sep 2006 |
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EP |
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11-010194 |
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Jan 1999 |
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JP |
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10-0837698 |
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Jun 2008 |
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KR |
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2005/049511 |
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Jun 2005 |
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WO |
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2005/077834 |
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Aug 2005 |
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WO |
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2008/108599 |
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Sep 2008 |
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WO |
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2009/031796 |
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Mar 2009 |
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WO |
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Other References
International Search Report and Written Opinion mailed Feb. 9,
2012, issued in corresponding International Application No.
PCT/US2011/036514, filed May 13, 2011, 11 pages. cited by applicant
.
International Search Report and Written Opinion mailed May 1, 2012,
issued in related International Application No. PCT/US2011/049769,
filed Aug. 30, 2011, 9 pages. cited by applicant .
International Preliminary Report on Patentability mailed Jan. 11,
2013, issued in related International Application No.
PCT/US2011/049769, filed Aug. 30, 2011, 4 pages. cited by applicant
.
International Search Report and Written Opinion mailed Apr. 20,
2012, issued in related International Application No.
PCT/US2011/049784, filed Aug. 30, 2011, 9 pages. cited by applicant
.
International Preliminary Report on Patentability mailed Mar. 14,
2013, issued in related International Application No.
PCT/US2011/049784, filed Aug. 30, 2011, 8 pages. cited by applicant
.
International Search Report and Written Opinion mailed Oct. 4,
2012, issued in related International Application No.
PCT/US2012/023882, filed Feb. 3, 2012, 7 pages. cited by
applicant.
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Primary Examiner: Barry; Chester
Attorney, Agent or Firm: Christensen O'Connor Johnson
Kindness PLLC
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a continuation of International Application No.
PCT/US2011/036514, filed May 13, 2011, which claims the benefit of
U.S. Patent Application No. 61/334,328, filed May 13, 2010, and
U.S. Patent Application No. 61/378,300, filed Aug. 30, 2010, each
expressly incorporated herein by reference in its entirety.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A method for producing inorganic phosphorus from wastewater,
comprising: (a) thickening a phosphorus- and magnesium-containing
mixture derived from microorganisms induced to release phosphorus
and magnesium to provide a phosphorus- and magnesium-rich liquid
and a phosphorus- and magnesium-reduced mixture; (b) conducting the
phosphorus- and magnesium-rich liquid to a first inorganic
phosphorus reactor; (c) anaerobically treating the phosphorus- and
magnesium-reduced mixture to provide an ammonia-rich, phosphorus-
and magnesium-reduced mixture; (d) separating a first ammonia-rich,
phosphorus- and magnesium-reduced liquid from the ammonia-rich,
phosphorus- and magnesium-reduced mixture; (e) conducting the first
ammonia-rich, phosphorus- and magnesium-reduced liquid to a second
inorganic phosphorus reactor to provide inorganic phosphorus and a
second ammonia-rich, phosphorus- and magnesium-reduced liquid; and
(f) adding ammonia to the phosphorus- and magnesium-rich liquid in
the first inorganic phosphorus reactor to provide inorganic
phosphorus.
2. The method of claim 1, wherein the ammonia added to the
phosphorus- and magnesium-rich liquid in the first inorganic
phosphorus reactor is derived from the second ammonia-rich,
phosphorus- and magnesium-reduced liquid.
3. The method of claim 1, wherein the ammonia added to the
phosphorus- and magnesium-rich liquid in the first inorganic
phosphorus reactor is derived from the inorganic phosphorus
provided in the second inorganic phosphorus reactor.
4. The method of claim 1, wherein the ammonia added to the
phosphorus- and magnesium-rich liquid in the first inorganic
phosphorus reactor is from an external source.
5. The method of claim 1, wherein the ammonia added to the
phosphorus- and magnesium-rich liquid in the first inorganic
phosphorus reactor is an ammonia-rich, phosphorus- and
magnesium-reduced liquid from the second inorganic phosphorus
reactor.
6. A method for treating wastewater and producing inorganic
phosphorus, comprising: (a) inducing a mixture of microorganisms
containing phosphorus and magnesium to release phosphorus and
magnesium to provide a treated mixture that includes phosphorus and
magnesium; (b) thickening the treated mixture to provide a
phosphorus- and magnesium-rich liquid and a phosphorus- and
magnesium-reduced mixture; (c) conducting the phosphorus- and
magnesium-rich liquid to a first inorganic phosphorus reactor; (d)
anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture; (e) separating a first ammonia-rich,
phosphorus- and magnesium-reduced liquid from the ammonia-rich,
phosphorus- and magnesium-reduced mixture; (f) conducting the first
ammonia-rich, phosphorus- and magnesium-reduced liquid to a second
inorganic phosphorus reactor to provide inorganic phosphorus and a
second ammonia-rich, phosphorus- and magnesium-reduced liquid; (g)
conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to an ammonia stripper to provide ammonia
and an ammonia-reduced, phosphorus-, and magnesium-reduced liquid;
and (h) adding the ammonia to the phosphorus- and magnesium-rich
liquid in the first inorganic phosphorus reactor to provide
inorganic phosphorus.
7. The method of claim 6 further comprising adjusting the pH of the
ammonia-rich, phosphorus- and magnesium-reduced liquid in the
second inorganic phosphorus reactor.
8. The method of claim 6 further comprising adding magnesium to the
ammonia-rich, phosphorus- and magnesium-reduced liquid in the
second inorganic phosphorus reactor.
9. The method of claim 6, wherein the inorganic phosphorus is a
magnesium/phosphate complex.
10. The method of claim 6, wherein the inorganic phosphorus is a
magnesium ammonium phosphate hexahydrate.
11. The method of claim 6, wherein the inorganic phosphorus is
struvite.
12. A method for treating wastewater and producing inorganic
phosphorus, comprising: (a) inducing a mixture of microorganisms
containing phosphorus and magnesium to release phosphorus and
magnesium to provide a treated mixture that includes phosphorus and
magnesium; (b) thickening the treated mixture to provide a
phosphorus- and magnesium-rich liquid and a phosphorus- and
magnesium-reduced mixture; (c) conducting the phosphorus- and
magnesium-rich liquid to a first inorganic phosphorus reactor; (d)
anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture; (e) separating a first ammonia-rich,
phosphorus- and magnesium-reduced liquid from the ammonia-rich,
phosphorus- and magnesium-reduced mixture; (f) conducting the first
ammonia-rich, phosphorus- and magnesium-reduced liquid to a second
inorganic phosphorus reactor to provide inorganic phosphorus; and
(g) conducting a portion of the inorganic phosphorus from the
second inorganic phosphorus reactor to a heater to provide
magnesium, phosphorus, and ammonia and water, wherein the ammonia
is added to the phosphorus- and magnesium-rich liquid in the first
inorganic phosphorus reactor to provide inorganic phosphorus.
13. The method of claim 12, wherein the ammonia and optionally
water from the heater are conducted to a separator to provide
gaseous ammonia, which is then optionally combined with water, and
added to the phosphorus- and magnesium-rich liquid in the first
inorganic phosphorus reactor.
14. The method of claim 12 further comprising adding magnesium to
the ammonia-rich, phosphorus- and magnesium-reduced liquid in the
second inorganic phosphorus reactor.
15. The method of claim 14, wherein the magnesium is provided from
the inorganic phosphorus in the heater to the second inorganic
phosphorus reactor.
16. The method of claim 12 further comprising adding phosphorus to
the ammonia-rich, phosphorus- and magnesium-reduced liquid in the
second inorganic phosphorus reactor.
17. The method of claim 16, wherein the phosphorus is provided from
the inorganic phosphorus in the heater to the second inorganic
phosphorus reactor.
18. The method of claim 12 further comprising conducting a portion
of the inorganic phosphorus from the first inorganic phosphorus
reactor to the heater.
19. A method for treating wastewater and producing inorganic
phosphorus, comprising: (a) inducing a mixture of microorganisms
containing phosphorus and magnesium to release phosphorus and
magnesium to provide a treated mixture that includes phosphorus and
magnesium; (b) thickening the treated mixture to provide a
phosphorus- and magnesium-rich liquid and a phosphorus- and
magnesium-reduced mixture; (c) conducting the phosphorus- and
magnesium-rich liquid to a first inorganic phosphorus reactor; (d)
adding ammonia to the phosphorus- and magnesium-rich liquid in the
first inorganic phosphorus reactor to provide inorganic phosphorus;
(e) anaerobically treating the phosphorus- and magnesium-reduced
mixture from step (b) to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture; (f) separating a first ammonia-rich,
phosphorus- and magnesium-reduced liquid from the ammonia-rich,
phosphorus- and magnesium-reduced mixture; and (g) conducting the
first ammonia-rich, phosphorus- and magnesium-reduced liquid to a
second inorganic phosphorus reactor to provide inorganic
phosphorus.
20. A method for treating wastewater and producing inorganic
phosphorus, comprising: (a) inducing a mixture of microorganisms
containing phosphorus and magnesium to release phosphorus and
magnesium to provide a treated mixture that includes phosphorus and
magnesium; (b) separating the treated mixture into a phosphorus-
and magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture; (c) conducting the phosphorus- and magnesium-rich liquid
to a first inorganic phosphorus reactor; (d) anaerobically treating
the phosphorus- and magnesium-reduced mixture to provide an
ammonia-rich, phosphorus- and magnesium-reduced mixture; (e)
separating the ammonia-rich, phosphorus- and magnesium-reduced
mixture to provide biosolids and a first ammonia-rich, phosphorus-
and magnesium-reduced liquid; (f) conducting the first
ammonia-rich, phosphorus- and magnesium-reduced liquid to a second
inorganic phosphorus reactor to provide inorganic phosphorus and a
second ammonia-rich, phosphorus- and magnesium-reduced liquid; and
(g) conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to the first inorganic phosphorus reactor
to provide inorganic phosphorus and a third ammonia-rich,
phosphorus- and magnesium-reduced liquid.
21. A system for producing inorganic phosphorus from wastewater,
comprising: (a) a first solids separator for thickening a
phosphorus- and magnesium-containing mixture; (b) a first inorganic
reactor, the reactor having a conduit for receiving ammonia; (c) a
first conduit intermediate the first solids separator and the first
inorganic phosphorus reactor; (d) a digester; (e) a second conduit
intermediate the first solids separator and the digester; (f) a
second solids separator; (g) a third conduit intermediate the
digester and the second solids separator; (h) a second inorganic
reactor; and (i) a fourth conduit intermediate the second solids
separator and the second inorganic phosphorus reactor.
22. The method of claim 20, wherein a portion of the ammonia-rich,
phosphorus- and magnesium-reduced liquid produced from the second
inorganic phosphorus reactor is conducted to the first reactor.
23. The method of claim 20 further comprising adjusting the pH of
the first ammonia-rich, phosphorus- and magnesium-reduced liquid in
the second inorganic phosphorus reactor.
24. The method of claim 20 further comprising adding magnesium to
the first ammonia-rich, phosphorus- and magnesium-reduced liquid in
the second inorganic phosphorus reactor.
25. The method of claim 20 further comprising adding phosphorus to
the first ammonia-rich, phosphorus- and magnesium-reduced liquid in
the second inorganic phosphorus reactor.
26. The method of claim 20 further comprising adding ammonia to the
first ammonia-rich, phosphorus- and magnesium-reduced liquid in the
second inorganic phosphorus reactor.
27. The method of claim 20 further comprising adjusting the pH of
the second ammonia-rich, phosphorus- and magnesium-reduced liquid
in the first inorganic phosphorus reactor.
28. The method of claim 20 further comprising adding magnesium to
the second ammonia-rich, phosphorus- and magnesium-reduced liquid
in the first inorganic phosphorus reactor.
29. The method of claim 1, wherein the inorganic phosphorus is
struvite.
30. The method of claim 12, wherein the inorganic phosphorus is
struvite.
31. The method of claim 19, wherein the inorganic phosphorus is
struvite.
32. The method of claim 20, wherein the inorganic phosphorus is
struvite.
33. The system of claim 21, wherein the first solids separator
further comprises a conduit for receiving a phosphorus- and
magnesium-containing mixture.
34. The system of claim 21, wherein the second solids separator
further comprises a conduit for conducting biosolids from the
solids separator.
35. The system of claim 21 further comprising: (a) an ammonia
stripper intermediate the first and second inorganic phosphorus
reactors; (b) a conduit intermediate the second inorganic
phosphorus reactor and the stripper; and (c) a conduit intermediate
the stripper and the first inorganic phosphorus reactor and the
stripper.
36. The system of claim 21 further comprising: (a) a heater
intermediate the first and second inorganic phosphorus reactors;
(b) a conduit intermediate the second inorganic phosphorus reactor
and the heater; (c) an ammonia separator intermediate the first and
second inorganic phosphorus reactors; (d) a conduit intermediate
the heater and the separator; and (e) a conduit intermediate the
separator and first inorganic phosphorus reactor.
37. The system of claim 21, wherein the second inorganic phosphorus
reactor further comprises a conduit for conducting an ammonia-rich,
phosphorus- and magnesium-reduced liquid from the second inorganic
phosphorus reactor.
38. The system of claim 21, wherein the first inorganic phosphorus
reactor further comprises a conduit for receiving ammonia.
39. The system of claim 21 further comprising a conduit
intermediate the second inorganic phosphorus reactor and the first
inorganic phosphorus reactor.
40. The system of claim 21 further comprising a conduit for
conducting a phosphorus- and magnesium-reduced liquid from the
first inorganic phosphorus reactor.
Description
FIELD OF THE INVENTION
The present invention relates in general to wastewater treatment
and processes and systems for recovery of phosphorus from
wastewater and for producing inorganic phosphorus complexes.
BACKGROUND OF THE INVENTION
The presence of dissolved phosphate in industrial effluents and
wastewater is a long-standing problem in the art. Phosphorus
(referred to herein as "P") is a non-renewable resource and an
important non-substitutable macronutrient, existing in nature as
phosphates in various inorganic or organic forms, and ranging from
the simple to the very complex in terms of molecular structure.
Because P is essential for all biological processes, there is
concern that the current demand and exploitation (total annual
production is about 20 million tons of P, derived from roughly 140
million tons of rock concentrates) of this non-renewable resource
is not sustainable. Nearly all the P used globally is mined from a
relatively small number of commercially-exploitable deposits, and
it has been estimated that the global economic P reserves may last
about 100 years at the current rate of extraction. Therefore, the
world's P resources are finite and should be used efficiently and
in a sustainable way. Additionally, aside from the non-renewable
resource aspect, there is need to improve P management,
particularly from the environment protection perspective because,
for example, P-enrichment in receiving waters is associated with
harmful algae blooms that affect the health and vitality of
wetlands and marine environments. Therefore, there is a pronounced
need in the art to develop methods for increasing the life
expectancy of the world's limited P resources. There is a
pronounced need in the art to develop methods for recovery and
recycling of P from industrial effluents and wastewater.
Art-recognized P removal technologies applied to wastewater include
chemical and biological processes. One chemical technology for P
removal and recovery is crystallization of P in the form of
struvite (magnesium ammonium phosphate hexahydrate or
MgNH.sub.4PO.sub.4.6H.sub.2O). Struvite is crystalline and thus
well suited for formation from effluent streams. In addition, as a
granular product struvite is more compact than other chemical
precipitates, and it performs well as a slow-release fertilizer.
Struvite formation requires reaction between three soluble ions in
solution, Mg.sup.2+, NH.sub.4.sup.+ and PO.sub.4.sup.3-, to form
precipitates with low solubility (struvite has a pK.sub.sp of
12.6). Struvite precipitation is controlled by pH, supersaturation,
and presence of impurities, such as calcium. High pH (e.g., pH 8.5)
and supersaturation of the three ions are favorable to struvite
formation.
As part of secondary sewage treatment, primary treated sewage is
treated with air or oxygen. In the activated sludge process,
microorganisms utilize oxygen to metabolize the incoming waste
sewage thereby forming a mixture of microorganisms and sewage
(mixed liquor). This mixture is conducted to settling tanks for
concentration to provide concentrated activated sludge. A majority
of the sludge is returned to the activated sludge process and a
separate portion of this sludge (waste activated sludge) is removed
from the activated sludge process and conducted to a sludge
handling system for further treatment and disposal.
In a typical wastewater treatment process, waste activated sludge
is conducted to a first centrifuge (or other thickening apparatus)
for thickening, where the liquids are tapped off and returned to
the wastewater plant for treatment and the resultant thickened
sludge is conducted to an anaerobic digester with other sludge
where it remains for a period of time before being conducted to a
second centrifuge (or other dewatering apparatus) for dewatering.
Struvite tends to form in the digester and other downstream
equipment because of the ammonia, magnesium and phosphorus present
in the process streams. This struvite is impractical to harvest and
also has the deleterious effect of being deposited on surfaces in
the process system components. The second centrifuge (or other
dewatering apparatus) produces additional dewatered sludge and
liquids that are rich in ammonia and phosphorus.
U.S. Pat. No. 7,604,740 describes a wastewater treatment method. In
the method, a first mixture of waste solids and microorganisms
containing phosphorus and magnesium are treated by first inducing
the mixture microorganisms to release phosphorus and magnesium that
is then tapped off as the mixture is thickened, to produce
phosphorus and magnesium-rich liquid and phosphorus and
magnesium-reduced treated mixture. The treated mixture is placed in
an anaerobic digester where ammonia is formed, but sparingly
combines with phosphorus or magnesium because the concentration of
these materials has been greatly reduced. Next, the high-ammonia
mixture is dewatered to produce an ammonia-rich liquid. Struvite is
then formed by combining the ammonia-rich liquid with the
phosphorus and magnesium-rich liquid. However, controlling the
formation of struvite through the combination of two variable
process streams is problematic.
Despite the advances in removing phosphorus from wastewater through
the formation and recovery of struvite, a need exists for improved
methods and devices for wastewater treatment and struvite recovery
that does not involve combining two variable process streams. The
present invention seeks to fulfill this need and provides further
related advantages.
SUMMARY OF THE INVENTION
The present invention provides methods and systems for treating
wastewater and producing inorganic phosphorus. In the methods and
systems, inorganic phosphorus is formed from phosphorus in the
wastewater by the combination of a phosphorus- and magnesium-rich
liquid stream with ammonia. The phosphorus- and magnesium-rich
liquid stream is a direct product from the release of phosphorus
and magnesium from phosphorus- and magnesium-containing
microorganisms in the wastewater. The ammonia that is combined with
the phosphorus- and magnesium-rich liquid stream is not an
untreated ammonia-rich liquid process stream, for example, an
ammonia-rich, phosphorus- and magnesium-reduced liquid obtained by
solids separation of the output from anaeronbic digestion of a
phosphorus- and magnesium-reduced mixture. Rather the ammonia that
is combined with the phosphorus- and magnesium-rich liquid stream
is either ammonia from an external source or derived from an
ammonia-rich process stream conducted from an inorganic phosphorus
reactor, optionally further treated by, for example, stripping or
separating ammonia from the stream.
In one aspect, the invention provides a method for producing
inorganic phosphorus from wastewater. In one embodiment, the method
comprises:
(a) thickening a phosphorus- and magnesium-containing mixture
derived from microorganisms induced to release phosphorus and
magnesium to provide a phosphorus- and magnesium-rich liquid and a
phosphorus- and magnesium-reduced mixture;
(b) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(c) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(d) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
to provide inorganic phosphorus and a second ammonia-rich,
phosphorus- and magnesium-reduced liquid; and
(f) adding ammonia to the phosphorus- and magnesium-rich liquid in
the first inorganic phosphorus reactor to provide inorganic
phosphorus.
In one embodiment, the ammonia added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor is
derived from the second ammonia-rich, phosphorus- and
magnesium-reduced liquid.
In one embodiment, the ammonia added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor is
derived from the inorganic phosphorus provided in the second
inorganic phosphorus reactor.
In one embodiment, the ammonia added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor is
from an external source.
In one embodiment, the ammonia added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor is
an ammonia-rich, phosphorus- and magnesium-reduced liquid from the
second inorganic phosphorus reactor.
In another embodiment, the invention provides a method for treating
wastewater and producing inorganic phosphorus, comprising:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
and adjusting the pH to provide inorganic phosphorus and a second
ammonia-rich, phosphorus- and magnesium-reduced liquid;
(f) conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to an ammonia stripper to provide ammonia
and an ammonia-reduced, phosphorus-, and magnesium-reduced liquid;
and
(g) adding the ammonia to the phosphorus- and magnesium-rich liquid
in the first inorganic phosphorus reactor to provide inorganic
phosphorus.
In a further embodiment, the invention provides a method for
treating wastewater and producing inorganic phosphorus,
comprising:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
to provide inorganic phosphorus; and
(g) conducting a portion of the inorganic phosphorus from the
second inorganic phosphorus reactor to a heater to provide
magnesium, phosphorus, and ammonia and water, wherein the ammonia
and water are added to the phosphorus- and magnesium-rich liquid in
the first inorganic phosphorus reactor to provide inorganic
phosphorus.
In one embodiment, the ammonia and water from the heater are
conducted to a separator to provide gaseous ammonia, which is then
optionally combined with water, and added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus
reactor.
In another embodiment, the invention provides a method for treating
wastewater and producing inorganic phosphorus, comprising:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) adding ammonia to the phosphorus- and magnesium-rich liquid in
the first inorganic phosphorus reactor to provide inorganic
phosphorus;
(e) anaerobically treating the phosphorus- and magnesium-reduced
mixture from step (b) to provide a ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture; and
(g) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
to provide inorganic phosphorus.
In a further embodiment, the invention provides a method for
treating wastewater and producing inorganic phosphorus,
comprising:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) separating the treated mixture into a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating the ammonia-rich, phosphorus- and magnesium-reduced
mixture to provide biosolids and a first ammonia-rich, phosphorus-
and magnesium-reduced liquid;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
to provide inorganic phosphorus and to provide a second
ammonia-rich, phosphorus- and magnesium-reduced liquid; and
(g) conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to the first inorganic phosphorus reactor
to provide inorganic phosphorus and a phosphorus- and
magnesium-reduced liquid.
In one embodiment, the phosphorus- and magnesium-reduced liquid is
conducted to the process headworks.
In one embodiment, magnesium, ammonia, and pH boosters are
independently, optionally added to the first and/or second
inorganic phosphorus reactors.
The above methods can further include the step of collecting
inorganic phosphorus from the inorganic phosphorus reactors.
In the above methods, the inorganic phosphorus is a
magnesium/phosphate complex. In one embodiment, the inorganic
phosphorus is a magnesium ammonium phosphate hexahydrate, such as
struvite.
In another aspect, the invention provides systems for treating
wastewater and producing inorganic phosphorus.
In one embodiment, the system for producing inorganic phosphorus
from wastewater, comprises:
(a) a first solids separator for thickening a phosphorus- and
magnesium-containing mixture;
(b) a first inorganic reactor, the reactor having a conduit for
receiving ammonia;
(c) a first conduit intermediate the first solids separator and the
first inorganic phosphorus reactor;
(d) a digester;
(e) a second conduit intermediate the first solids separator and
the digester;
(f) a second solids separator;
(g) a third conduit intermediate the digester and the second solids
separator.
(h) a second inorganic reactor; and
(i) a fourth conduit intermediate the second solids separator and
the second inorganic phosphorus reactor.
In one embodiment, the first solids separator further comprises a
conduit for receiving a phosphorus- and magnesium-containing
mixture.
In one embodiment, the second solids separator further comprises a
conduit for conducting biosolids from the solids separator.
In one embodiment, the system further comprises:
(a) an ammonia stripper intermediate the first and second inorganic
phosphorus reactors;
(b) a conduit intermediate the second inorganic phosphorus reactor
and the stripper; and
(c) a conduit intermediate the stripper and the first inorganic
phosphorus reactor and the stripper.
In one embodiment, the system further comprises:
(a) a heater intermediate the first and second inorganic phosphorus
reactors;
(b) a conduit intermediate the second inorganic phosphorus reactor
and the heater;
(c) an ammonia separator intermediate the heater and the first
inorganic phosphorus reactor;
(d) a conduit intermediate the heater and the separator; and
(e) a conduit intermediate the separator and first inorganic
phosphorus reactor.
In one embodiment, the second inorganic phosphorus reactor further
comprises a conduit for conducting a second ammonia-rich,
phosphorus- and magnesium-reduced liquid from the second inorganic
phosphorus reactor, and the first inorganic phosphorus reactor
further comprises a conduit for receiving ammonia.
In one embodiment, the system further comprises a conduit
intermediate the second inorganic phosphorus reactor and the first
inorganic phosphorus reactor; and the first inorganic phosphorus
reactor further comprises a conduit for conducting a phosphorus-
and magnesium-reduced liquid from the reactor.
DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this
invention will become more readily appreciated as the same become
better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings.
FIG. 1 is a schematic illustration of a representative method of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 2 is a schematic illustration of a representative method of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 3 is a schematic illustration of a representative method of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 4 is a schematic illustration of a representative method of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 5 is a schematic illustration of a representative system of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 6 is a schematic illustration of a representative system of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 7 is a schematic illustration of a representative system of
the invention for treating wastewater and producing inorganic
phosphorus.
FIG. 8 is a schematic illustration of a representative system of
the invention for treating wastewater and producing inorganic
phosphorus.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides processes for removing and recovering of
phosphorus from wastewater through the formation of inorganic
phosphorus (e.g., struvite). The processes advantageously remove
phosphorus from wastewater treatment streams and provide inorganic
phosphorus as a valuable byproduct.
The present invention provides a method for handling nutrients in
wastewater with the goals of reducing phosphorus and magnesium in
the mixture fed to a wastewater digester and reducing struvite
scale formation in the digester where ammonia, a starting material
for making struvite, is released. Other objectives achieved by the
process include removing phosphorus from the system in mineral
(inorganic) form rather than biosolids to reduce volume and obtain
more valuable phosphorus-containing products; minimizing the
linking of different process streams for improved process
flexibility and ready recovery from upsets; and reducing ammonia
content in the final liquid.
As noted above, the present invention provides a method for
treating wastewater and producing inorganic phosphorus. In the
method, inorganic phosphorus is formed from phosphorus in the
wastewater by the combination of a phosphorus- and magnesium-rich
liquid stream with ammonia. The phosphorus- and magnesium-rich
liquid stream is a direct product from the release of phosphorus
and magnesium from phosphorus- and magnesium-containing
microorganisms in the wastewater. The ammonia that is combined with
the phosphorus- and magnesium-rich liquid stream is not an
ammonia-rich liquid stream, as in the process described in U.S.
Pat. No. 7,604,740. Rather the ammonia that is combined with the
phosphorus- and magnesium-rich liquid stream is either ammonia from
an external source or derived from an ammonia-rich process stream
from an inorganic phosphorus reactor, optionally further treated
by, for example, stripping or separating ammonia from an
ammonia-rich process. By the use of ammonia, rather than an
ammonia-rich process stream, as a feedstock in the formation of
inorganic phosphorus, the method of the invention provided improved
control over the inorganic phosphorus formation reaction.
In the methods and systems of the invention, ammonia is combined
with phosphorus and magnesium to produce inorganic phosphorus
(e.g., struvite). It will be appreciated that the nature of the
ammonia will depend on the pH of the environment of the process
streams in which the ammonia is present. For example, at lower pH,
ammonia will be in the form of ammonium (NH.sub.4.sup.+) and can be
associated with counterions (e.g., sulfate, SO.sub.4.sup.2-).
A schematic illustration of a first embodiment of the method of the
invention for treating wastewater and producing inorganic
phosphorus is shown in FIG. 1. Referring to FIG. 1, a mixture of
microorganisms containing phosphorus and magnesium are induced to
release phosphorus and magnesium into liquid to provide a treated
mixture that includes phosphorus and magnesium. The treated mixture
is then thickened (dewatered) to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture. The phosphorus- and magnesium-rich liquid is conducted to
a first inorganic phosphorus reactor. The phosphorus- and
magnesium-reduced mixture is subjected to anaerobic digestion,
where ammonia is released, to provide a first ammonia-rich,
phosphorus- and magnesium-reduced mixture containing suspended
solids in liquid. At this point substantially no combination of
phosphorus and magnesium occurs because of the relatively low
concentration of each and because the pH is low. The first
ammonia-rich, phosphorus- and magnesium-reduced liquid is separated
from the ammonia-rich, phosphorus- and magnesium-reduced mixture
leaving behind a high biosolids portion. Separation of the liquid
from the biosolids can be achieved by a variety of conventional
means including gravity belts, filters, and centrifuges. The
biosolids are removed from the system and the first ammonia-rich,
phosphorus- and magnesium-reduced liquid is conducted to a second
inorganic phosphorus reactor for inorganic phosphorus formation.
There, magnesium is added, if needed, and pH is adjusted (e.g.,
addition of sodium hydroxide or other suitable pH booster), if
necessary to provide inorganic phosphorus (e.g., struvite) and a
second ammonia-rich, phosphorus- and magnesium-reduced liquid. The
inorganic phosphorus is collected from the reactor and the high pH,
second ammonia-rich, phosphorus- and magnesium-reduced liquid is
conducted to an ammonium stripper, where the pH is adjusted as
necessary (e.g., addition of sodium hydroxide or other suitable pH
booster). The stripper provides a low ammonia, high pH liquid,
which is removed from the system, and ammonia gas that is
introduced into the first inorganic phosphorus reactor where it is
combined with the phosphorus- and magnesium-rich liquid produced
from the thickening of the treated mixture containing phosphorus
and magnesium from the microorganism release step. As an
alternative to introducing ammonia gas to the first inorganic
phosphorus reactor, ammonia gas from the stripper can be combined
with water and the resulting water containing ammonia can be added
to the first reactor. In one embodiment, the ammonia stripper
operating in combination with sulfuric acid provides ammonium
sulfate combined in water as the ammonia source. Inorganic
phosphorus (e.g., struvite) is formed in and ultimately collected
from the first reactor. Additional ammonia or other suitable pH
boosters can be added to the first reactor, as necessary. In one
embodiment, a phosphorus- and magnesium-reduced liquid produced by
the first reactor is conducted from the reactor.
The above method decouples the phosphorus- and magnesium-rich
liquid from the ammonia-rich liquid (compare with U.S. Pat. No.
7,604,740 where the two process streams are combined) in the
inorganic phosphorus forming step, which provides for greater
process operational flexibility and increased process control.
Because either stream can be subject to variations and upsets,
their decoupling allows for each inorganic phosphorus reactor to be
unaffected by perturbations in the other's process streams.
Thus, in one embodiment, the method includes the following
steps:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
(optionally adjusting pH and optionally adding magnesium) to
provide inorganic phosphorus (e.g., struvite) and a second
ammonia-rich, phosphorus- and magnesium-reduced liquid;
(g) conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to an ammonia stripper to provide ammonia
and an ammonia-reduced, phosphorus-, and magnesium-reduced liquid;
and
(h) adding the ammonia produced in step (f) to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor to
provide inorganic phosphorus (e.g., struvite).
The above process offers advantages over conventional methods for
recovering phosphorus from wastewater. For example, the addition of
caustic in the second crystallizer (second inorganic phosphorus
reactor) reduces the amount needed to be added in the stripper. The
process also allows for the option of capturing at least a portion
of the ammonia as ammonium sulfate, which is a useful fertilizer,
because it is possible the ammonia demand by the first crystallizer
will be less than that produced by the stripper. The ammonia
addition to the first crystallizer can replace most or all of the
caustic needed there, because in addition to providing the ammonia
needed stoichiometrically for the reaction, it also is a powerful
pH booster in this pH range. Ammonia (e.g., gas) from external
sources can also be used to feed the first crystallizer.
A schematic illustration of a second embodiment of the method of
the invention for treating wastewater and producing inorganic
phosphorus is shown in FIG. 2. Referring to FIG. 2, a mixture of
microorganisms containing phosphorus and magnesium are induced to
release phosphorus and magnesium into liquid to provide a treated
mixture that includes phosphorus and magnesium. The treated mixture
is then thickened (dewatered) to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture. The phosphorus- and magnesium-rich liquid is conducted to
a first inorganic phosphorus reactor. The phosphorus- and
magnesium-reduced mixture is subjected to anaerobic digestion,
where ammonia is released, to provide an ammonia-rich, phosphorus-
and magnesium-reduced mixture containing suspended solids in
liquid. Substantially no combination of phosphorus and magnesium
occurs at this point because of the relatively low concentration of
each and because the pH is low. A first ammonia-rich, phosphorus-
and magnesium-reduced liquid is separated from the ammonia-rich,
phosphorus- and magnesium-reduced mixture leaving behind a high
biosolids portion. As noted above, separation of the liquid from
the biosolids can be achieved by a variety of conventional means.
The biosolids are removed from the system and the first
ammonia-rich, phosphorus- and magnesium-reduced liquid is conducted
to a second inorganic phosphorus reactor for inorganic phosphorus
formation. There, phosphorus and/or magnesium is added, if needed
(the sources for the phosphorus and magnesium are either external
or from the inorganic phosphorus heater described below), and pH is
adjusted (e.g., addition of sodium hydroxide or other suitable pH
booster), if necessary, to provide inorganic phosphorus (e.g.,
struvite) and a second ammonia-rich, phosphorus- and
magnesium-reduced liquid, which is removed from the system. The
inorganic phosphorus is collected from the reactor and optionally
directed to an inorganic phosphorus heater that provides ammonia
and water, and magnesium, phosphorus, and water vapor. The water
vapor is exhausted from the system and the magnesium and the
phosphorus are conducted to the first inorganic phosphorus reactor
to serve as inputs, as necessary. The ammonia and water are either
converted for other uses (e.g., combined with sulfuric acid to
provide ammonium sulfate, which can be added to inorganic
phosphorus to provide a nitrogen boost) or directed to a separator
to provide ammonia gas. The ammonia is then introduced into the
first inorganic phosphorus reactor where it is combined with the
phosphorus- and magnesium-rich liquid produced from the thickening
of the treated mixture containing phosphorus and magnesium from the
microorganism release step. Inorganic phosphorus (e.g., struvite)
is formed in and ultimately collected from the first reactor. As an
alternative to introducing ammonia gas to the first inorganic
phosphorus reactor, ammonia gas from the stripper can be combined
with water and the resulting water containing ammonia can be added
to the first reactor. Alternatively, the water and ammonia from the
heater can be used in a combined form (i.e., concentrated
ammonia/water liquid mixture) thereby obviating the need for the
separator. Additional ammonia (e.g., gas from external source) or
other suitable pH boosters can be added to the first reactor, as
necessary. Inorganic phosphorus formed in the first reactor can be
optionally directed to the inorganic phosphorous heater to provide
magnesium and phosphorus conducted to the first inorganic
phosphorus reactor. In one embodiment, a phosphorus- and
magnesium-reduced liquid produced by the first reactor is conducted
from the reactor.
Thus, in one embodiment, the method includes the following
steps:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
and optionally adjusting the pH (and optionally adding magnesium
and/or phosphorus) to provide inorganic phosphorus (e.g.,
struvite);
(g) conducting a portion of the inorganic phosphorus from the
second inorganic phosphorus reactor to a heater to provide
magnesium, phosphorus, and ammonia and water,
wherein the magnesium and phosphorus are optionally conducted to
the second inorganic phosphorus reactor, and
wherein the ammonia and water are added to the phosphorus- and
magnesium-rich liquid in the first inorganic phosphorus reactor
(optionally adjusting pH) to provide inorganic phosphorus (e.g.,
struvite); and
(h) optionally conducting a portion of the inorganic phosphorus
from the second inorganic phosphorus reactor to the heater in step
(g).
In one embodiment, the ammonia and water are conducted to a
separator to provide gaseous ammonia, which is optionally combined
with water, that is added to the phosphorus- and magnesium-rich
liquid in the first inorganic reactor.
Advantages of the process of the second embodiment include those
noted above with regard to process of the first embodiment relating
to the advantage associated with ammonia use. A further advantage
of the process of the second embodiment is the additional recovery
and re-use of magnesium, which can be used in the formation of
inorganic phosphorus.
A schematic illustration of a third embodiment of the method of the
invention for treating wastewater and producing inorganic
phosphorus is shown in FIG. 3. Referring to FIG. 3, a mixture of
microorganisms containing phosphorus and magnesium are induced to
release phosphorus and magnesium into liquid to provide a treated
mixture that includes phosphorus and magnesium. The treated mixture
is then thickened (dewatered) to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture. The phosphorus- and magnesium-rich liquid is conducted to
a first inorganic phosphorus reactor. The phosphorus- and
magnesium-reduced mixture is subjected to anaerobic digestion,
where ammonia is released, to provide an ammonia-rich, phosphorus-
and magnesium-reduced mixture. Substantially no combination of
phosphorus and magnesium occurs because of the relatively low
concentration of each and because the pH is low. A first
ammonia-rich, phosphorus- and magnesium-reduced liquid is separated
from the ammonia-rich, phosphorus- and magnesium-reduced mixture
leaving behind a high biosolids portion. As noted above, separation
of the liquid from the biosolids can be achieved by a variety of
conventional means. The biosolids are removed from the system and
the first ammonia-rich, phosphorus- and magnesium-reduced liquid is
conducted to a second inorganic phosphorus reactor, where magnesium
is added, if needed, and pH is adjusted (e.g., addition of sodium
hydroxide or other suitable pH booster), if necessary, to provide
inorganic phosphorus (e.g., struvite). The inorganic phosphorus is
collected from the reactor and the high pH, second ammonia-rich,
phosphorus- and magnesium-reduced liquid is removed from the
system. Ammonia (e.g., gas) is introduced into a first inorganic
phosphorus reactor where it is combined with the phosphorus- and
magnesium-rich liquid produced from the thickening of the treated
mixture containing phosphorus and magnesium from the microorganism
release step. Inorganic phosphorus (e.g., struvite) is formed in
and ultimately collected from the first reactor. Other suitable pH
boosters can be added to the first reactor, as necessary. In one
embodiment, a phosphorus- and magnesium-reduced liquid produced by
the first reactor is conducted from the reactor.
Thus, in one embodiment, the method includes the following
steps:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) adding ammonia to the phosphorus- and magnesium-rich liquid in
the first inorganic phosphorus reactor (optionally adjusting pH) to
provide inorganic phosphorus (e.g., struvite);
(e) anaerobically treating the phosphorus- and magnesium-reduced
mixture from step (b) to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture; and
(g) conducting the ammonia-rich, phosphorus- and magnesium-reduced
liquid to a second inorganic phosphorus reactor and optionally
adjusting the pH (and optionally adding magnesium, phosphorus,
and/or ammonia, each from an external source) to provide inorganic
phosphorus (e.g., struvite).
Advantages of the process of the third embodiment include those
noted above with regard to process of the first and second
embodiments relating to the advantage associated with ammonia use.
A further advantage of the process of the third embodiment is the
further decoupling of the two crystallizers and the greater
production of useful struvite.
A schematic illustration of a fourth embodiment of the method of
the invention for treating wastewater and producing inorganic
phosphorus is shown in FIG. 4. Referring to FIG. 4, a mixture of
microorganisms containing phosphorus and magnesium are induced to
release phosphorus and magnesium into liquid to provide a treated
mixture that includes phosphorus and magnesium. The treated mixture
is then thickened (dewatered) to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture. The phosphorus- and magnesium-rich liquid is conducted to
a first inorganic phosphorus reactor. The phosphorus- and
magnesium-reduced mixture is subjected to anaerobic digestion,
where ammonia is released, to provide an ammonia-rich, phosphorus-
and magnesium-reduced mixture. Substantially no combination of
phosphorus and magnesium occurs because of the relatively low
concentration of each and because the pH is low. A first
ammonia-rich, phosphorus- and magnesium-reduced liquid is separated
from the ammonia-rich, phosphorus- and magnesium-reduced mixture
leaving behind a high biosolids portion. As noted above, separation
of the liquid from the biosolids can be achieved by a variety of
conventional means. The biosolids are removed from the system and
the first ammonia-rich, phosphorus- and magnesium-reduced liquid is
conducted to a second inorganic phosphorus reactor, where magnesium
is added, if needed, and pH is adjusted (e.g., addition of sodium
hydroxide or other suitable pH booster), if necessary, to provide
inorganic phosphorus (e.g., struvite). The inorganic phosphorus is
collected from the reactor and the high pH, second ammonia-rich,
phosphorus- and magnesium-reduced liquid is conducted to the first
inorganic phosphorus reactor where it is combined with the
phosphorus- and magnesium-rich liquid produced from the thickening
of the treated mixture containing phosphorus and magnesium from the
microorganism release step. Inorganic phosphorus (e.g., struvite)
is formed in and ultimately collected from the first reactor. Other
suitable pH boosters and magnesium can be added to the first
reactor, as necessary. In one embodiment, a phosphorus- and
magnesium-reduced liquid produced by the first reactor is conducted
from the reactor.
Thus, in one embodiment, the method includes the following
steps:
(a) inducing a mixture of microorganisms containing phosphorus and
magnesium to release phosphorus and magnesium to provide a treated
mixture that includes phosphorus and magnesium;
(b) thickening the treated mixture to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(c) conducting the phosphorus- and magnesium-rich liquid to a first
inorganic phosphorus reactor;
(d) anaerobically treating the phosphorus- and magnesium-reduced
mixture from step (b) to provide an ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(e) separating a first ammonia-rich, phosphorus- and
magnesium-reduced liquid from the ammonia-rich, phosphorus- and
magnesium-reduced mixture;
(f) conducting the first ammonia-rich, phosphorus- and
magnesium-reduced liquid to a second inorganic phosphorus reactor
and optionally adjusting the pH (and optionally adding magnesium,
phosphorus, and/or ammonia, each from an external source) to
provide inorganic phosphorus (e.g., struvite) and a second
ammonia-rich, phosphorus- and magnesium-reduced liquid; and
(g) conducting the second ammonia-rich, phosphorus- and
magnesium-reduced liquid to the first inorganic phosphorus reactor
(optionally adjusting pH) to provide inorganic phosphorus (e.g.,
struvite).
For the methods described herein in which an ammonia-rich,
phosphorus- and magnesium-reduced liquid produced from the second
inorganic phosphorus reactor is conducted to the first reactor, it
will be appreciated that the amount of ammonia required for
inorganic phosphorus production in the first inorganic reactor may
be less than the amount of ammonia present in the ammonia-rich,
phosphorus- and magnesium-reduced liquid produced from the second
inorganic phosphorus reactor. Accordingly, in some embodiments,
only a portion of the ammonia-rich, phosphorus- and
magnesium-reduced liquid produced from the second inorganic
phosphorus reactor is conducted to the first reactor.
In another aspect, the invention provides systems for treating
wastewater and producing inorganic phosphorus.
Referring to FIG. 5, in one embodiment, the system (500) for
producing inorganic phosphorus from wastewater, comprises:
(a) a first solids separator (110) for thickening a phosphorus- and
magnesium-containing mixture derived from microorganisms induced to
release phosphorus and magnesium to provide a phosphorus- and
magnesium-rich liquid and a phosphorus- and magnesium-reduced
mixture;
(b) a first inorganic reactor (120) for producing inorganic
phosphorus;
(c) a first conduit (520) intermediate the first solids separator
and the first inorganic phosphorus reactor for conducting the
phosphorus- and magnesium-rich liquid to the first inorganic
phosphorus reactor;
(d) a digester (130) for anaerobically treating the phosphorus- and
magnesium-reduced mixture to provide an ammonia-rich, phosphorus-
and magnesium-reduced mixture;
(e) a second conduit (530) intermediate the first solids separator
and the digester for conducting the phosphorus- and
magnesium-reduced mixture to the digester;
(f) a second solids separator (140) for separating a first
ammonia-rich, phosphorus- and magnesium-reduced liquid from the
ammonia-rich, phosphorus- and magnesium-reduced mixture;
(g) a second inorganic reactor (150) for producing inorganic
phosphorus; and
(h) a third conduit (540) intermediate the second solids separator
and the second inorganic phosphorus reactor for conducting the
first ammonia-rich, phosphorus- and magnesium-reduced liquid to the
second inorganic phosphorus reactor.
In one embodiment, the first solids separator further comprises a
conduit (510) for receiving a phosphorus- and magnesium-containing
mixture.
In one embodiment, the second solids separator further comprises a
conduit (550) for conducting biosolids from the solids
separator.
In one embodiment, the first reactor further comprises a conduit
(590) for conducting a phosphorus- and magnesium-reduced liquid
from the reactor
In one embodiment, the system (500) further comprises:
(a) an ammonia stripper (160) intermediate the first and second
inorganic phosphorus reactors;
(b) a conduit (570) intermediate the second inorganic phosphorus
reactor and the stripper for conducting a second ammonia-rich,
phosphorus- and magnesium-reduced liquid from the second inorganic
phosphorus reactor to the stripper; and
(c) a conduit (580) intermediate the stripper and the first
inorganic phosphorus reactor and the stripper for conducting
ammonia from the stripper to the first inorganic phosphorus
reactor. See FIGS. 1 and 5.
In one embodiment, the system further comprises:
(a) a heater intermediate the first and second inorganic reactors
for producing ammonia and water from inorganic phosphorus from the
second inorganic phosphorus reactor;
(b) a conduit intermediate the second inorganic phosphorus reactor
and the heater for conducting inorganic phosphorus from the second
inorganic phosphorus reactor to the heater;
(c) a separator intermediate the heater and the first inorganic
reactor for producing ammonia from the ammonia and water produced
by the heater;
(d) a conduit intermediate the heater and the separator for
conducting ammonia and water from the heater to the separator;
and
(e) a conduit intermediate the separator and first inorganic
phosphorus reactor for conducting ammonia from the separator to the
first inorganic phosphorus reactor. See FIGS. 2 and 6.
Referring to FIG. 6, system 600 includes:
(a) a first solids separator (110);
(b) a first inorganic reactor (120);
(c) a first conduit (620) intermediate the first solids separator
and the first inorganic phosphorus reactor;
(d) a digester (130);
(e) a second conduit (630) intermediate the first solids separator
and the digester;
(f) a second solids separator (140);
(g) a third conduit (640) intermediate the digester and the second
solids separator;
(h) a second inorganic reactor (150);
(i) a third conduit (660) intermediate the second solids separator
and the second inorganic phosphorus reactor;
(j) a heater (170) for producing ammonia and water from inorganic
phosphorus from the second inorganic phosphorus reactor;
(k) a conduit (675) intermediate the second inorganic phosphorus
reactor and the heater for conducting inorganic phosphorus from the
second inorganic phosphorus reactor to the heater;
(l) a separator (180) for producing ammonia from the ammonia and
water produced by the heater;
(m) a conduit (685) intermediate the heater and the separator for
conducting ammonia and water from the heater to the separator;
and
(n) a conduit (695) intermediate the separator and first inorganic
phosphorus reactor for conducting ammonia from the separator to the
first inorganic phosphorus reactor.
In one embodiment, the first solids separator further comprises a
conduit (610) for receiving a phosphorus- and magnesium-containing
mixture.
In one embodiment, the second solids separator further comprises a
conduit (650) for conducting biosolids from the solids
separator.
In one embodiment, the first reactor further comprises a conduit
(696) for conducting a phosphorus- and magnesium-reduced liquid
from the reactor.
In another embodiment, the second inorganic phosphorus reactor
further comprises a conduit for conducting a second ammonia-rich,
phosphorus- and magnesium-reduced liquid from the second inorganic
phosphorus reactor, and the first inorganic phosphorus reactor
further comprises a conduit for receiving ammonia and a conduit for
conducting a phosphorus- and magnesium-reduced liquid from the
reactor. See FIGS. 3 and 7.
Referring to FIG. 7, system 700 includes:
(a) a first solids separator (110);
(b) a first inorganic reactor (120);
(c) a first conduit (720) intermediate the first solids separator
and the first inorganic phosphorus reactor;
(d) a digester (130);
(e) a second conduit (730) intermediate the first solids separator
and the digester;
(f) a second solids separator (140);
(g) a third conduit (740) intermediate the digester and the second
solids separator;
(h) a second inorganic reactor (150); and
(i) a third conduit (760) intermediate the second solids separator
and the second inorganic phosphorus reactor.
In one embodiment, the first solids separator further comprises a
conduit (710) for receiving a phosphorus- and magnesium-containing
mixture.
In one embodiment, the second solids separator further comprises a
conduit (750) for conducting biosolids from the solids
separator.
In one embodiment, the first reactor further comprises a conduit
(780) for conducting a phosphorus- and magnesium-reduced liquid
from the reactor.
In a further embodiment, the system further comprises a conduit
intermediate the second inorganic phosphorus reactor and the first
inorganic phosphorus reactor for conducting a second ammonia-rich,
phosphorus- and magnesium-reduced liquid from the second inorganic
phosphorus reactor to the first inorganic phosphorus reactor; and
the first inorganic phosphorus reactor further comprises a conduit
for conducting a phosphorus- and magnesium-reduced liquid from the
first inorganic phosphorus reactor. See FIGS. 4 and 8.
Referring to FIG. 8, system 800 includes:
(a) a first solids separator (110);
(b) a first inorganic reactor (120);
(c) a first conduit (820) intermediate the first solids separator
and the first inorganic phosphorus reactor;
(d) a digester (130);
(e) a second conduit (830) intermediate the first solids separator
and the digester;
(f) a second solids separator (140);
(g) a third conduit (840) intermediate the second solids separator
and the second inorganic phosphorus reactor;
(h) a second inorganic reactor (150);
(i) a third conduit (860) intermediate the second solids separator
and the second inorganic phosphorus reactor; and
(j) a conduit (870) intermediate the second inorganic phosphorus
reactor and the first inorganic phosphorus reactor for conducting a
second ammonia-rich, phosphorus- and magnesium-reduced liquid from
the second inorganic phosphorus reactor to the first inorganic
phosphorus reactor.
In one embodiment, the first solids separator further comprises a
conduit (810) for receiving a phosphorus- and magnesium-containing
mixture.
In one embodiment, the second solids separator further comprises a
conduit (850) for conducting biosolids from the solids
separator.
In one embodiment, the first reactor further comprises a conduit
(880) for conducting a phosphorus- and magnesium-reduced liquid
from the reactor.
While illustrative embodiments have been illustrated and described,
it will be appreciated that various changes can be made therein
without departing from the spirit and scope of the invention.
* * * * *